Disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and embedded servo sectors. The embedded servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo controller to control the velocity of the actuator arm as it seeks from track to track.
Certain types of heads (e.g., magnetoresistive heads) comprise a read element radial offset from a write element. The radial offset may span a fraction of a track, or several tracks plus a fraction of a track. To account for this radial offset, a jog value is typically added to the servo system either during write or read operations. There is, therefore, a need to calibrate the jog value by estimating the radial offset between the read element and write element.